US6769044B2 - Input/output interface and semiconductor integrated circuit having input/output interface - Google Patents

Input/output interface and semiconductor integrated circuit having input/output interface Download PDF

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US6769044B2
US6769044B2 US10/003,048 US304801A US6769044B2 US 6769044 B2 US6769044 B2 US 6769044B2 US 304801 A US304801 A US 304801A US 6769044 B2 US6769044 B2 US 6769044B2
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circuit
signal
input
signals
transmitting
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US20030016056A1 (en
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Yasurou Matsuzaki
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Socionext Inc
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Fujitsu Ltd
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    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F13/00—Interconnection of, or transfer of information or other signals between, memories, input/output devices or central processing units
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L25/00—Baseband systems
    • H04L25/38—Synchronous or start-stop systems, e.g. for Baudot code
    • H04L25/40—Transmitting circuits; Receiving circuits
    • H04L25/49—Transmitting circuits; Receiving circuits using code conversion at the transmitter; using predistortion; using insertion of idle bits for obtaining a desired frequency spectrum; using three or more amplitude levels ; Baseband coding techniques specific to data transmission systems
    • H04L25/493—Transmitting circuits; Receiving circuits using code conversion at the transmitter; using predistortion; using insertion of idle bits for obtaining a desired frequency spectrum; using three or more amplitude levels ; Baseband coding techniques specific to data transmission systems by transition coding, i.e. the time-position or direction of a transition being encoded before transmission
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03M—CODING; DECODING; CODE CONVERSION IN GENERAL
    • H03M5/00—Conversion of the form of the representation of individual digits
    • H03M5/02—Conversion to or from representation by pulses

Definitions

  • the present invention relates to an input/output interface for transmitting/receiving a transmission signal between semiconductor integrated circuits or inside the semiconductor integrated circuit.
  • a transmission signal is transmitted/received by turning a signal line into a high level or a low level corresponding to a binary number.
  • one-bit data is transmitted by one signal line.
  • the number of the signal lines increases as the bit number of the transmission signal to be transmitted increases.
  • the chip size of the semiconductor integrated circuit increases or the area of a system board increases as the transmission amount increases.
  • input/output circuits for inputting/outputting data to/from the signal line are necessary for each bit.
  • the number of the input/output circuits increases, which causes the disadvantage that charging/discharging currents due to switching increase.
  • a consumption current increases as a bit width of the data increases.
  • the data amount handled by portable equipment such as a cellular phone which uses a battery as its power source has been increasing substantially. The increase of the data amount is an important issue because it has a significant influence on the operating time of the portable equipment like the above.
  • Japanese Unexamined Patent Application Publication No. Hei 5-227035 Japanese Unexamined Patent Application Publication No. Hei 10-107684.
  • the logical value is expressed by the pulse width of the pulse signal and the combination of the timings that the transition edges appear.
  • the four parameters T 1 to T 4 are necessary in order to express two-bit data, and hence the structures of the transmitting circuit and the receiving circuit are complicated. Further, since the timing margin is necessary for each of the parameters T 1 to T 4 , the timing design of the transmitting circuit and the receiving circuit is difficult. For this reason, it is necessary to increase the cycle time of the pulse signal.
  • the digital data is expressed by the time difference which is generated by the frame signals being adjacent timewise, in the spread spectrum communication system.
  • this kind of communication system has the complex transmitting/receiving circuits and its power consumption is large.
  • a logical value is expressed by an order that transition edges appear in a plurality of transmission signals transmitting respectively on a plurality of signal lines. For this reason, a large amount of data can be transmitted through the small number of the signal lines according to the combination of the timings that the transition edges appear in the transmission signals. Since a large amount of data can be transmitted by one transmission, it is possible to substantially increase the data transfer rate.
  • the logic can be expressed by a difference in timings that the transition edges appear (relative value), and hence a standard signal is not necessary. In other words, it is not necessary to synchronize the standard signal between the transmitting side and the receiving side of the transmission signal.
  • a transmitting circuit and a receiving circuit of the transmission signal can be simplified.
  • the transmitting circuit for transmitting the transmission signal and the receiving circuit for receiving the transmission signal are formed on separate semiconductor chips, whereby the number of the signal lines to be wired between the semiconductor chips can be reduced.
  • the semiconductor chips are mounted on a printed-wiring board, the area of the signal lines on the printed-wiring board can be reduced. As a result of this, the size of the printed-wiring board is reduced, which makes it possible to reduce the size of a system and reduce the cost of the system.
  • the transmitting circuit for transmitting the transmission signal and the receiving circuit for receiving the transmission signal are formed on the same semiconductor chip, whereby the wiring area inside the semiconductor chip can be reduced. As a result of this, the chip size of the semiconductor chip can be reduced and the chip cost can be reduced.
  • each of the transmission signals include a plurality of the transition edges, and the logical value is expressed by combining the order that the respective transition edges appear in the transmission signals. Hence, a larger amount of data can be transmitted.
  • a logical value is expressed by using the order that the transition edges appear in pulse signals.
  • only leading edges or trailing edges of the pulse signals, or both of the leading edges and the trailing edges of the pulse signals may be used.
  • 576 patterns of logic can be expressed by using four signal lines. This exceeds nine-bit binary data (512 patterns). Since the signal lines are structured by three lines or more, the data can be transmitted more efficiently than in the case of transmitting the binary data as it is.
  • the present invention is applied to transmission signals with larger bit numbers in general, such as data or addresses, it is possible to reduce the number of bus lines substantially, so that power consumption can be substantially reduced and the size of the device can be reduced.
  • a transmitting circuit includes, for example, a delay circuit which includes a plurality of delay stages connected in cascade, a selecting circuit and an edge generator.
  • the delay circuit the standard signal is received on an initial stage of the delay stages and the standard signal is delayed and outputted as a timing signal from each delay stage.
  • the selecting circuit selects any one of the timing signals for each signal line, according to a logical value.
  • the edge generator generates a transition edge for each transmission signal, in synchronization with each of the selected timing signals. A large amount of data can be transmitted by structuring simple logic circuits like the above.
  • the delay circuit for outputting the timing signals respectively for the leading edges and the trailing edges, and a first and a second selecting circuits for the leading edges and the trailing edges.
  • an output resistor of an open drain type is formed in the edge generator, whereby a plurality of the transmitting circuits can be connected to the bus line.
  • the receiving circuit includes a comparing circuit including a plurality of comparators and a logical value generating circuit including a decoder.
  • the comparing circuit compares the order that the transition edges appear in the transmission signals.
  • Each comparator is structured by a flip-flop or the like which receives the two different transmission signals.
  • the logical value generating circuit decodes the result of the comparison by the comparing circuit, and generates the logical value based on the result of the decoding.
  • the receiving circuit may restore the original logical value which is transferred from the transmitting circuit, or it may generate a logical value (for example, inverting logic) which is different from the logical value transferred from the transmitting circuit.
  • a large amount of data can be transmitted by structuring simple logic circuits like the above.
  • a logical value is expressed by a time difference between a transition edge of a transmission signal transmitting on a signal line and the transition edge of a standard timing signal. For this reason, the logical values consisting of a plurality of bits can be transferred by one signal line. Namely, a large amount of data can be transmitted by a small number of the signal lines. Since a large amount of data can be transmitted by one transmission, it is possible to substantially increase the data transfer rate. Therefore, it is possible to reduce the number of the signal lines as compared with the conventional art.
  • the transmitting circuit converts the respective logical values, expressed with a plurality of bits, to predetermined delay time.
  • Each logical value is outputted as the transmission signal, which is behind the standard timing signal by the delay time, where the output is made to the signal line.
  • the receiving circuit detects the time that the transition edge of the transmission signal transmitting through the signal line is delayed, compared to the transition edge of the standard timing signal, and generates the logical value according to the delay time.
  • the transmitting circuit needs to delay the transmission signal by the delay time corresponding to the logical value.
  • the receiving circuit can generate a logical value only by detecting the time that the transmission signal is delayed, compared to the transition edge of the standard timing signal.
  • the logical value can be converted to the transmission signal by the simple transmitting circuit and the transmission signal can be converted to a logical value by the simple receiving circuit.
  • the receiving circuit may restore the original logical value which is transferred from the transmitting circuit, or it may generate the logical value (for example, inverting logic) which is different from the logical value transferred from the transmitting circuit.
  • the present invention is applied to transmission signals with larger bit numbers in general, such as data or addresses, it is possible to reduce the number of the bus lines substantially, so that the power consumption can be substantially reduced and the size of the device can be reduced.
  • a variable delay circuit may be formed in the transmitting circuit and a delay time of the variable delay circuit may be changed according to the logical value, thereby generating the transmission signal to be transmitted.
  • the delay circuit for generating the plurality of the timing signals whose phases are different from that of the standard timing signal, and a comparing circuit for comparing the phase of the received transmission signal and the phase of each timing signal and for detecting the delay time of the transmission signal to the standard timing signal may be formed in the receiving circuit, thereby generating the logical value with ease.
  • a plurality of latch circuits for latching logic levels of the transmission signals by each timing signal are formed in the comparing circuit so that the phase of the transmission signal can be expressed by logic levels to be latched in each latch circuit.
  • a simple encoder is formed in the comparing circuit so that the logical value can be generated based on the logic levels being latched in the latch circuits.
  • the transmitting circuit and the receiving circuit are formed on separate semiconductor chips, whereby the number of signal lines to be wired between the semiconductor chips can be reduced.
  • the semiconductor chips are mounted on the printed-wiring board, the area of the signal lines on the printed-wiring board can be reduced. As a result of this, the size of the printed-wiring board is reduced, which makes it possible to reduce the size of the system and reduce the cost of the system.
  • the transmitting circuit and the receiving circuit are formed on the same semiconductor chip so that the wiring area inside the semiconductor chip can be reduced. As a result of this, the chip size of the semiconductor chip can be reduced, and the chip cost can be reduced.
  • the transmitting circuit and the receiving circuit are respectively formed on a plurality of semiconductor chips, the data can be transmitted/received by a small number of signal lines.
  • a first input circuit and a second input circuit for receiving a transmission signal and a standard timing signal which is outputted from another semiconductor chip, respectively, are formed for receiving the transmission signal, and a first output circuit for outputting another transmission signal, a signal generating circuit for generating another standard timing signal according to an external clock signal and a second output circuit for outputting the standard timing signal to the exterior of the chip are formed for transmitting the transmission signal, in each semiconductor chip.
  • an input of the first input circuit and an output of the first output circuit are connected to a common external terminal and the signal line is allowed to transmit the transmission signal bidirectionally, so that the number of the signal lines can be further reduced.
  • an input of the second input circuit and an output of the second output circuit are connected to a common external terminal and the signal line is allowed to transmit the transmission signal bidirectionally, so that the number of the signal lines can be further reduced.
  • FIG. 1 is an explanatory view showing the first basic principle in the present invention
  • FIG. 2 is a block diagram showing the details of a transmitting circuit in the first embodiment of the present invention
  • FIG. 3 is a block diagram showing the predecoder in FIG. 1;
  • FIG. 4 is a conversion table for converting a logic value to a signal which is output to the data bus line;
  • FIG. 5 is a circuit diagram showing the details of the decoder DEC 1 and selector SEL 1 in FIG. 2;
  • FIG. 6 is a circuit diagram showing the details of the decoder DEC 5 and selector SEL 5 in FIG. 2;
  • FIG. 7 is a circuit diagram showing the details of the edge generating unit in the edge generator in FIG. 2;
  • FIG. 8 is a block diagram showing the details of a receiving circuit in the first embodiment of the present invention.
  • FIG. 9 is a circuit diagram showing the details of the comparator in FIG. 8;
  • FIG. 10 is a conversion table for restoring a signal, which is output into the data bus line, to a original logic value
  • FIG. 11 is a circuit diagram showing the details of the decoder in FIG. 8;
  • FIG. 12 is a circuit diagram showing the details of the decoder in FIG. 8;
  • FIG. 13 is an explanatory view showing the second basic principle in the present invention.
  • FIG. 14 is a block diagram showing the second embodiment of the present invention.
  • FIG. 15 is a circuit diagram showing the details of a transmitting circuit in FIG. 14;
  • FIG. 16 is a circuit diagram showing the details of the delay circuit and latch circuit in the receiving circuit in FIG. 14;
  • FIG. 17 is a circuit diagram showing the details of the encoder in the receiving circuit in FIG. 14;
  • FIG. 18 is a timing chart showing the operation of the transmitting circuit and receiving circuit in the second embodiment
  • FIG. 19 is a block diagram showing the third embodiment of the present invention.
  • FIG. 20 is a block diagram showing the fourth embodiment of the present invention.
  • FIG. 21 is a block diagram showing the fifth embodiment of the present invention.
  • FIG. 1 shows the first basic principle in the present invention.
  • an example of transmitting data from a transmitting device 10 to a receiving device 12 by using four data bus lines (signal lines) DA, DB, DC, and DD will be explained.
  • a data transmitting circuit 14 in the transmitting device 10 outputs low level pulses (hereinafter referred to as the L-pulses) to the data bus lines DA, DB, DC, and DD.
  • Logical values of the data are expressed by an order that transition edges appear in the L-pulses. Namely, combinations of leading edges (down edges) of the L-pulses express 24 patterns of logic, and additionally, combinations of trailing edges (up edges) of the L-pulses express 24 patterns of the logic. By combining the leading edges and the trailing edges, 576 patterns of the logic can be expressed. This exceeds nine-bit binary data (512 patterns). In other words, in this invention, the data whose amount is larger than nine bits can be transmitted only by using the four data bus lines DA, DB, DC, and DD.
  • a minimum interval between the leading edges of the transmission signals to be outputted to the data bus lines DA to DD and a minimum interval between the trailing edges thereof are set as tD 1
  • an interval between the leading edge and the trailing edge which are nearest to each other is set as tD 2 .
  • the interval tD 1 is set as the value by which the order of the transition edges can be judged
  • the interval tD 2 is set as the value by which the leading edge and the trailing edge can be identified even in the transmission signal with the smallest pulse width.
  • the intervals tD 1 and tD 2 are set according to the characteristics of the transmitting circuit 14 , a receiving circuit 16 and transmission lines (the data bus lines DA to DD in this example).
  • the data receiving circuit 16 in the receiving device 12 judges the orders that the leading edges and the trailing edges appear in the transmission signals which are transmitted through the data bus lines DA, DB, DC, and DD, and generates the logical values. It should be mentioned that the receiving circuit 16 may restore the logical values (original logical values) which are used in the transmitting device 10 , or it may generate logical values (for example, inverting data of the original logical values) which are specially used in the receiving device 12 .
  • 14400 patterns ((5 ⁇ 4 ⁇ 3 ⁇ 2) 2 ) of the logic can be expressed by using five data bus lines. This exceeds 13-bit binary data (8192 patterns).
  • FIG. 2 to FIG. 12 show a first embodiment of an input/output interface and a semiconductor integrated circuit according to the present invention.
  • Signal lines shown by bold lines in the drawings mean that each of these is structured by a plurality of the lines.
  • the input/output interface is structured by the data transmitting circuit 14 in the transmitting device 10 , the data receiving circuit 16 in the receiving device 12 , and the data bus lines DA, DB, DC, and DD for transferring the data from the transmitting device 10 to the receiving device 12 , as shown in FIG. 1 .
  • the transmitting device 10 is a microcomputer and the receiving device 12 is a semiconductor memory device such as DRAM.
  • the transmitting device 10 and the receiving device 12 are mounted on a system board or the like as separate semiconductor chips. Signal lines for transmitting a control signal and an address signal which are not shown in FIG. 1 are wired between the transmitting device 10 and the receiving device 12 .
  • FIG. 2 shows the details of the transmitting circuit 14 in the transmitting device 10 .
  • the transmitting circuit 14 includes a predecoder 18 , a delay circuit 20 , selecting circuits 22 , 24 and an edge generator 26 .
  • the predecoder 18 decodes logical values D8 to D0 consisting of nine bits and outputs a decoding signal.
  • the delay circuit 20 includes seven delay stages 20 a which are connected in cascade. An initial stage of the delay stages 20 a on receives a standard signal STD.
  • the standard signal STD is a high-level pulse signal.
  • Each delay stage 20 a delays the standard signal STD in sequence and outputs it as timing signals N 2 to N 8 . Further, the delay circuit 20 outputs the standard signal STD as a timing signal N 1 .
  • the delay circuit 20 operates as a timing signal generator for generating a plurality of the timing signals N 1 to N 8 whose transition edges are different from each other.
  • Each of the numerals tD 1 and tD 2 shown in the respective delay stages 20 a is the interval (delay time of the delay stage 20 a ) in FIG. 1 .
  • the first selecting circuit 22 is the circuit for setting the timing of the leading edges of the L-pulse signals which are outputted from the transmitting circuit 14 .
  • the first selecting circuit 22 includes decoders DEC 1 to DEC 4 and selectors SEL 1 to SEL 4 .
  • the decoders DEC 1 to DEC 4 generate selecting signals for operating the selectors SEL 1 to SEL 4 by using the decoding signal.
  • the logic of the decoders DEC 1 to DEC 4 are decided corresponding to a later-described conversion table. According to the selecting signal, the selectors SEL 1 to SEL 4 respectively output the timing signals N 1 to N 4 to any of nodes NDD, NCD, NBD, and NAD.
  • the second selecting circuit 24 is the circuit for setting the timing of the trailing edges of the L-pulse signals which are outputted from the transmitting circuit 14 .
  • the second selecting circuit 24 includes decoders DEC 5 to DEC 8 and selectors SEL 5 to SEL 8 .
  • the decoders DEC 5 to DEC 8 generate selecting signals for operating the selectors SEL 5 to SEL 8 by using the decoding signal.
  • the logic of the decoders DEC 5 to DEC 8 are decided corresponding to the later-described conversion table.
  • the selectors SEL 5 to SEL 8 respectively output the timing signals N 5 to N 8 to any of the nodes NDD, NCD, NBD, and NAD.
  • the nodes NDD, NCD, NBD, and NAD are the nodes which correspond to the data bus lines DD, DC, DB, and DA, respectively.
  • the edge generator 26 includes four edge generating units 26 a which correspond to the nodes NDD, NCD, NBD, and NAD, respectively.
  • the edge generating units 26 a generate the leading edges of the L-pulse signals which are outputted to the data bus lines DD, DC, DB, and DA, in synchronization with the timing signals N 1 to N 4 which are transmitted to the nodes NDD, NCD, NBD, and NAD, respectively.
  • the edge generating units 26 a generate the trailing edges of the L-pulse signals which are outputted to the data bus lines DD, DC, DB, and DA, in synchronization with the timing signals N 5 to N 8 which are transmitted to the nodes NDD, NCD, NBD, and NAD, respectively.
  • FIG. 3 shows the details of the predecoder 18 in FIG. 2 .
  • the predecoder 18 includes a decoding circuit for generating four decoding signals according to the logical values D8 to D7 a decoding circuit for generating four decoding signals according to the logical values D6 to D5, a decoding circuit for generating two decoding signals according to the logical value D4, a decoding circuit for generating two decoding signals according to the logical value D3, a decoding circuit for generating four decoding signals according to the logical values D2 to D1, and a decoding circuit for generating two decoding signals according to the logical value D0 .
  • the symbol “/” in the drawing shows a negative logic.
  • FIG. 4 is a conversion table for converting the logical values D8 to D0 of nine bits to the L-pulse signals which are outputted to the data bus lines DA to DD.
  • “Order of edges” show the orders that the leading edges or the trailing edges appear in the L-pulse signals to be outputted to the data bus lines DA to DD.
  • “ABCD” in the number 0 means that the leading edges (or the trailing edges) of the L-pulse signals change in the order of the data bus lines DA, DB, DC, and DD
  • BADC in the number 7 means that the leading edges (or the trailing edges) of the L-pulse signals change in the order of the data bus lines DB, DA, DD, and DC.
  • the data is transferred by using the four data bus lines DA to DD, as explained with reference to FIG. 1 .
  • the data is transferred by using the four data bus lines DA to DD, as explained with reference to FIG. 1 .
  • the four data bus lines DA to DD there are 24 possible combinations each for the leading edges and the trailing edges of the L-pulse signals, which are from the number 0 to the number 23.
  • 576 patterns of the logical values can be expressed by the four L-pulse signals.
  • the logic L 1 is used when the logical values D8 to D0 are “000000000” to “101111111”, and the logic L 2 is used when the logical values D8 to D0 are “110000000” to “111111111”.
  • the logical values D8 to D0 “001011000” are included in the logic L 1 .
  • the order of the leading edges becomes “ADCB” in the number 5
  • the order of the trailing edges becomes “BCAD” in the number 8.
  • the logical values D8 to D0 “111010011” are included in the logic L 2 .
  • the order of the leading edges becomes “ADCB” in the number 5
  • the order of the trailing edges becomes “DACB” in the number 19.
  • the conversion table is not limited to the FIG. 4 .
  • Other conversion tables may be formed by changing the correspondence between the logical values D8 to D0 and the order of the edges.
  • FIG. 5 shows the details of the decoder DEC 1 and the selector SEL 1 shown in FIG. 2 .
  • the decoder DEC 1 turns any of its four outputs into the high level according to the logical values D8 to D0 to be transferred.
  • the selector SEL 1 turns on any of four CMOS transmission gates which respectively connect the signal line of the timing signal N 1 and the nodes NAD to NDD, according to an output signal from the decoder DEC 1 .
  • the timing signal N 1 is outputted to any of the nodes NAD to NDD in accordance with the conversion table shown in FIG. 4 .
  • the decoder DEC 1 shown in FIG. 5 is only one example for realizing the logic in the conversion table in FIG. 4 with a relatively small number of elements.
  • the decoders DEC 2 to DEC 4 and the selectors SEL 2 to SEL 4 are structured similarly to the decoder DEC 1 and the selector SEL 1 .
  • FIG. 6 shows the details of the decoder DEC 5 and the selector SEL 5 shown in FIG. 2 .
  • the decoder DECS turns any of its four outputs into the high level according to the logical values D8 to D0 to be transferred.
  • the selector SEL 5 turns on any of four CMOS transmission gates which respectively connect the signal line of the timing signal N 5 and nodes NAU to NDU, according to an output signal from the decoder DEC 5 .
  • the timing signal N 5 is outputted to any of the nodes NAU to NDU in accordance with the conversion table shown in FIG. 4 .
  • FIG. 7 shows the details of the edge generating unit 26 a in the edge generator 26 shown in FIG. 2 .
  • the edge generating unit 26 a includes an L-pulse generator for generating the L-pulse in synchronization with a rising edge of any of the timing signals N 1 to N 4 which is transmitted to the node NAD (or NBD, NCD, or NDD), an H-pulse generator for generating an H-pulse signal in synchronization with a rising edge of any of the timing signals N 5 to N 8 which is transmitted to the node NAU (or NBU, NCU, or NDU), a pMOS transistor (which is controlled by an output of the L-pulse generator) and an nMOS transistor (which is controlled by an output of the H-pulse generator) which are connected in series between a power source line and a ground line, a latch circuit for latching outputs of the pMOS transistor and the nMOS transistor, and an output transistor (output circuit) of an open drain type
  • the data bus line DA (or DB, DC, or DD) is turned into a low level in synchronization with the rising edge of any of the timing signals N 1 to N 4 , and turned into the high level in synchronization with the rising edge of any of the timing signals N 5 to N 8 . That is, the L-pulse signals whose leading edges and trailing edges synchronize to the selected timing signals are outputted to the data bus lines DA to DD. As a result of this, 512 patterns of the logical values D8 to D0 can be transmitted only by using the four data bus lines DA to DD.
  • FIG. 8 shows the details of the receiving circuit 16 in the receiving device 12 .
  • the receiving circuit 16 includes an input circuit 28 , comparing circuits 30 and 32 , transmitting circuits 34 , 36 and a decoder 38 .
  • the input circuit 28 includes four input buffers for receiving the L-pulse signals which are transmitted through the data bus lines DA to DD.
  • Each of the input buffers is structured by a differential amplifier, one of whose inputs receives the L-pulse signal and the other thereof receives a reference voltage VREF.
  • the input buffers respectively output the received signals as positive signals PA 2 , PB 2 , PC 2 , and PD 2 having positive logic.
  • the positive signals PA 2 , PB 2 , PC 2 , and PD 2 are inverted by inverters and outputted as negative signals NA 2 , NB 2 , NC 2 , and ND 2 having negative logic.
  • the comparing circuit 30 includes six comparators 30 b (second comparators) for comparing the orders that the trailing edges (up edges) appear in the two L-pulse signals. “(CD)” or the like shown in each comparator 30 b shows the alphabet of the data bus line to which the L-pulse signal compared by the comparator 30 b is transmitted. Each of the comparators 30 b outputs the result of the comparison as complementary signals.
  • the comparing circuit 32 includes six comparators 32 b (first comparators) for comparing the order that the leading edges (down edges) appear in the two L-pulse signals. “(CD)” or the like shown in each comparator 32 b shows the alphabet of the data bus line to which the L-pulse signal compared by the comparator 32 b is transmitted. Each of the comparators 32 b outputs the result of the comparison as complementary signals.
  • the transmitting circuit 34 transfers the complementary signals which are outputted from the comparators 30 b to the decoder 38 in synchronization with a transmitting signal TR 2 .
  • the transmitting signal TR 2 is generated by AND logic of the positive signals PA 2 , PB 2 , PC 2 , and PD 2 . Namely, the transmitting signal TR 2 is outputted in accordance with the trailing edge of the L-pulse signal with the latest timing, out of the four L-pulse signals.
  • the transmitting circuit 36 transfers the complementary signals which are outputted from the comparators 32 b to the decoder 38 in synchronization with a transmitting signal TR 1 .
  • the transmitting signal TR 1 is generated by AND operation of the negative signals NA 2 , NB 2 , NC 2 , and ND 2 . Namely, the transmitting signal TR 1 is outputted in accordance with the leading edge of the L-pulse signal with the latest timing, out of the four L-pulse signals.
  • complementary transmitting signals S 2 to 6 X and S 2 to 6 Z which are outputted from the transmitting circuit 34 are respectively turned into the low level and the high level, when the corresponding comparator 30 a judges that the timing that the trailing edge of the L-pulse signal appears on the data bus line DC is earlier than the timing that the trailing edge of the L-pulse signal appears on the data bus line DD.
  • each of the alphabets A, B, C, and D shown inside the frame of the decoder 38 means that the timing that the transitional edge of the L-pulse which corresponds to the alphabet appears is early when the transmitting signal from the transmitting circuits 34 and 36 shown by the alphabet is at a high level.
  • the alphabets A, B, C, and D respectively correspond to the L-pulse signals transmitting through the data bus lines DA, DB, DC, and DD.
  • the decoder 38 restores the logic which is transmitted from the transmitting circuit 14 according to the results of the comparison (transmitting signals) outputted from the comparators 30 b and 32 b , and outputs it as the logical values D8 to D0 .
  • FIG. 9 shows the details of the comparators 30 b and 32 b in FIG. 8 .
  • Each comparators 30 b and 32 b is structured by an RS flip-flop, in which inputs and outputs of NAND gates having two inputs are connected to each other. Outputs of the NAND gates are connected to output terminals through inverters. For example, when an input IN 1 changes to the high level first, outputs OUT 1 and OUT 2 are turned into the high level and the low level, respectively, and when an input IN 2 changes to the high level first, the outputs OUT 1 and OUT 2 are turned into the low level and the high level, respectively.
  • FIG. 10 is a conversion table for restoring the L-pulse signal which is received through the data bus lines DA to DD to the original logical values D8 to D0 . “No.”, “order of edges”, “logic 1” and “logic 2” are the same as those of the conversion table shown in FIG. 4 .
  • the outputs of the comparators 32 b and 30 b become “111000” and “001111”, respectively.
  • the output of the comparator 32 b “ 111000” shows the logic levels of the transmitting signals S 1 to 1 Z, S 1 to 2 Z, S 1 to 3 Z, S 1 to 4 Z, S 1 to 5 Z, and S 1 to 6 Z having the positive logic, as shown in FIG. 8 .
  • the output of the comparator 30 b “ 001111” shows the logic levels of the transmitting signals S 2 to 1 Z, S 2 to 2 Z, S 2 to 3 Z, S 2 to 4 Z, S 2 to 5 Z, and S 2 to 6 Z having the positive logic, as shown in FIG. 8 .
  • FIG. 11 and FIG. 12 show the details of the decoder 38 in FIG. 8 .
  • FIG. 11 shows a logic circuit for restoring the logical values D4 to D8 .
  • FIG. 12 shows a logic circuit for restoring the logical values D0 to D3.
  • the logic circuits like these are structured according to the conversion table in FIG. 10 .
  • Each logic circuit as shown in FIG. 11 and FIG. 12 is only one example for realizing the logic in the conversion table of FIG. 10 with the relatively small number of elements. There are many other circuits for realizing the same logic.
  • the logical values are expressed by the order that the transition edges appear in the plurality of the transmission signals transmitting respectively on the plurality of the data bus lines DA to DD.
  • a large amount of data can be transmitted by the small number of the signal lines. Since a large amount of data can be transmitted by one transmission of the transmission signals, it is possible to substantially increase a data transfer rate.
  • the order that a leading edge appears in and the order that a trailing edge appears in said pulse signal (the plurality of the transition edges) is used to express the logical values. For this reason, 576 patterns of the logic can be expressed by the four signal lines. This exceeds nine-bit binary data (512 patterns).
  • the logic can be expressed by a difference in timing that the transition edges appear (relative value), and hence the standard signal is not necessary. In other words, it is not necessary to synchronize the standard signal between the transmitting side and the receiving side of the transmission signal.
  • the structures of the transmitting circuit 14 and the receiving circuit 16 can be simplified.
  • the transmitting circuit 14 and the receiving circuit 16 are formed on the separate semiconductor chips.
  • the area of the signal lines on the printed-wiring board can be reduced.
  • the size of the printed-wiring board is reduced, which makes it possible to reduce the size of a system and reduce the cost of the system.
  • the logical values can be expressed by the order that the transition edges appear in the transmission signals, a large amount of data can be transmitted by structuring the simple logic circuits for both of the transmitting circuit 14 and the receiving circuit 16 .
  • the data transmitting circuit 14 of the transmitting device 10 may generate the L-pulse in accordance with the logical values of the data to be transferred.
  • the transmitting circuit 14 can be structured by the simple logic circuit.
  • the receiving circuit 16 in the receiving device 12 may compare the edges of the received signals and judge which edge is earlier.
  • the receiving circuit 16 can be structured by the simple logic circuit as well.
  • the circuit scales of the transmitting circuit 14 and the receiving circuit 16 can be reduced, and therefore, it is possible to reduce the chip size of the semiconductor integrated circuit to which the circuits like the above are mounted.
  • the output transistor of the open drain type is formed in the edge generator 26 , the plurality of the transmitting circuits 14 can be connected to the data bus lines DA to DD.
  • FIG. 13 shows the second basic principle in the present invention.
  • CLK clock signal line
  • the transmitting circuit 40 outputs a transmission signal SIG which is delayed for a predetermined time with reference to an up edge of the standard timing signal CLK.
  • the logical values of the data are expressed by delay time (time difference) of transition edges of the transmission signal SIG to transition edges of the standard timing signal CLK.
  • delay time time difference
  • four patterns of delay times are set so that the two-bit data can be transferred by one signal line.
  • the differences in timings that the transition edges appear in the transmission signals SIG are respectively set as 4 ns. This difference is set according to the characteristics of the transmitting circuit 40 , the receiving circuit 42 , and a transmission line (the data bus line DATA in this example).
  • the standard timing signal CLK and the transmission signals SIG are respectively generated by delaying the standard timing signal CLK itself for predetermined times according to the logical values.
  • the transition edges of the transmission signals SIG are delayed by, for example, 6 ns, 10 ns, 14 ns, and 18 ns, respectively, with reference to the transition edges of the standard timing signal CLK.
  • the receiving circuit 42 receives the standard timing signal CLK and the transmission signal SIG and detects the time difference (delay time) between the transition edges of the transmission signal SIG and the transition edges of the standard timing signal CLK. Then, the logical value is generated according to the difference. It should be mentioned that the receiving circuit 42 may restore the logical values (original logical values) which are used in the transmitting circuit 40 , or it may generate logical values (for example, inverting data of the original logical values) which are specially used in the receiving circuit 42 .
  • the data of a plurality of bits is transmitted/received by one data bus line DATA. Since the number of the data bus lines which are wired between the transmitting circuit 40 and the receiving circuit 42 can be reduced, it is possible to reduce the number of the input circuits and the output circuits of the data. As a result of this, the power consumption can be reduced. The number of the input circuits and the output circuits are reduced, and hence the chip size of the semiconductor integrated circuit to which these circuits are mounted can be reduced. Since the number of the data bus lines is reduced, it is possible to reduce the wiring area.
  • FIG. 14 shows a second embodiment of the input/output interface and the semiconductor integrated circuit according to the present invention.
  • Signal lines shown by bold lines in the drawing mean that each of these is structured by a plurality of the lines.
  • the input/output interface is structured by a transmitting circuit 40 , a receiving circuit 42 and a data bus line DATA as shown in FIG. 13 .
  • the transmitting circuit 40 and the receiving circuit 42 are formed inside the same semiconductor memory device (semiconductor integrated circuit) of a clock synchronous type.
  • the receiving circuit 42 is arranged near an output pad of data.
  • the transmitting circuit 40 receives data DT0 and DT1 of a plurality of bits, which are read from a memory core (not shown), and output a transmission signal SIG corresponding to the logic of the data to the data bus line DATA.
  • the receiving circuit 42 restores the transmission signal SIG which is received through the data bus line DATA to an original two-bit data, and outputs it to a data output circuit (peripheral circuit) or the like.
  • the data bus line DATA is wired from the end of the memory core to near the output pad, and its wiring is long.
  • the transmitting circuit 40 includes a decoder 44 , a variable delay circuit 46 , and an output part 48 .
  • the decoder 44 decodes the data DT0 and DT1 which are read from the memory core, and outputs the result of the decoding (corresponding to the logical values) to the variable delay circuit 46 .
  • the variable delay circuit 46 delays a standard timing signal TZ for a predetermined time according to the result of the decoding, and outputs the delayed signal to the output part 48 .
  • the output part 48 outputs the received signal to the data bus line DATA as the transmission signal SIG.
  • the standard timing signal TZ is, for example, an internal clock signal which synchronizes to a clock signal supplied from the exterior of the chip.
  • the receiving circuit 42 includes a delay circuit 50 , latches 52 a , 52 b , 52 c , and an encoder 54 .
  • the delay circuit 50 receives the standard timing signal TZ, and generates four timing signals TDZ 1 , TDZ 2 , TDZ 3 , and TDZ 4 whose phases are different from that of the standard timing signal TZ.
  • the latches 52 a , 52 b , and 52 c latch the transmission signal SIG in synchronization with the timing signals TDZ 1 , TDZ 2 , and TDZ 3 , respectively.
  • the encoder 54 generates logical values RDT0 and RDT1 consisting of two bits, in accordance with the logic levels of the transmission signal SIG which is latched by the latches 52 a , 52 b , and 52 c .
  • the logical values RDT1 and RDT2 are the same as the logical values DT0 and DT1.
  • the receiving circuit 42 restores the original data which is read from the memory core.
  • the logical values RDT0 and RDT1 which are generated in the receiving circuit 42 may be different from the original logical values DT0 and DT1.
  • the receiving circuit 42 may generate inverting logic of the original logical values.
  • the latches 52 a , 52 b , 52 c , and the encoder 54 operate as a comparing circuit which compares the phase of the transmission signal SIG transmitted from the transmitting circuit 40 and the timing signals TDZ 1 to TDZ 4 and detects the delay time of the transmission signal SIG with reference to the standard timing signal TZ.
  • the standard timing signal TZ is received by the receiving circuit 42 behind the standard timing signal TZ which is received by the transmitting circuit 40 , by the time corresponding to a load of the data bus line DATA.
  • FIG. 15 shows the details of the transmitting circuit 40 in FIG. 14 .
  • the decoder 44 receives the logical values DT0 and DT1, which are read from the memory core, through read amplifiers 40 a , and decodes the received data. Namely, any of decoding signals T 0 , T 1 , T 2 , and T 3 changes to the low level, in accordance with the logical values DT0 and DT1.
  • the variable delay circuit 46 includes four delay stages 46 a , 46 b , 46 c , and 46 d which are connected in cascade, and switching circuits 46 e , 46 f , 46 g , and 46 h which are respectively controlled by the decoding signals T 0 to T 3 .
  • the delay stages 46 a to 46 d respectively delay the standard timing signal TZ for predetermined times and output delay signals DLY 1 , DLY 2 , DLY 3 , and DLY 4 .
  • the delay time of each of the delay stages 46 a to 46 d is set at approximately 4 ns. Therefore, the delay signals DLY 1 to DLY 4 are delayed by 4 ns with reference to the standard timing signal TZ in sequence and outputted.
  • Each of the switching circuits 46 e to 46 h is structured by a CMOS transmission gate and an inverter for controlling the CMOS transmission gate.
  • one terminal receives the delay signals DLY 1 to DLY 4 , respectively, and the other terminal is connected to the output part 48 . Further, any of the delay signals DLY 1 to DLY 4 is outputted to the output part 48 according to the decoding signals T 0 to T 3 .
  • the output part 48 includes a latch circuit 48 a for latching the delay signal outputted from the variable delay circuit 46 and an output buffer 48 b .
  • the transmission signal SIG whose timing is shown in FIG. 13 is latched in the latch circuit 48 a and outputted from the output buffer 48 b.
  • FIG. 16 shows the details of the delay circuit 50 and the latch circuits 52 a , 52 b , and 52 c in the receiving circuit 42 in FIG. 14 .
  • the delay circuit 50 includes four delay stages 50 a , 50 b , 50 c , and 50 d which are connected in cascade.
  • the delay stages 50 a to 50 d respectively output the timing signals TDZ 1 , TDZ 2 , TDZ 3 , and TDZ 4 which are time signals respectively delayed from the standard timing signal TZ by predetermined time periods.
  • the delay time of the delay stage 50 a is set at approximately 8 ns and the delay time of each of the delay stages 50 b to 50 d is set at approximately 4 ns.
  • the timing signals TDZ 1 , TDZ 2 , TDZ 3 , and TDZ 4 are respectively delayed by 8 ns, 12 ns, 16 ns, and 20 ns to the standard timing signal TZ, and outputted.
  • Each of the latch circuits 52 a , 52 b , and 52 c is structured by a CMOS transmission gate, an inverter for controlling the CMOS transmission gate and a latch.
  • the latch circuit 52 a latches the logic level of the transmission signal SIG in synchronization with a rising edge of the timing signal TDZ 1 .
  • the latch circuit 52 b latches the logic level of the transmission signal SIG in synchronization with a rising edge of the timing signal TDZ 2 .
  • the latch circuit 52 c latches the logic level of the transmission signal SIG in synchronization with a rising edge of the timing signal TDZ 3 .
  • the high level is latched to the latch circuit.
  • the rising edge of the transmission signal SIG is later than the rising edge of the timing signal, the low level is latched to the latch circuit.
  • the timing signals TDZ 1 to TDZ 3 are respectively delayed by 8 ns, 12 ns, and 16 ns to the standard timing signal TZ, and the transmission signal SIG is delayed by any of 6 ns, 10 ns, 14 ns, and 18 ns to the standard timing signal TZ.
  • a timing margin for the latch circuits 52 a to 52 c to operate properly is set as 2 ns.
  • the data latched by the latch circuits 52 a to 52 c are respectively outputted as latch signals L 1 , L 2 , and L 3 and these inverting signals /L 1 , /L 2 , and /L 3 .
  • FIG. 17 shows the details of the encoder 54 in the receiving circuit 42 in FIG. 14 .
  • the encoder 54 includes a decoder 56 for decoding the latch signals L 1 , L 2 , L 3 , /L 1 , /L 2 , and /L 3 , and a data generator 58 for generating two-bit logical values in accordance with the result of the decoding by the decoder 56 .
  • the decoder 56 turns any of decoding signals T 5 , T 6 , T 7 , and T 8 into the low level according to the logical values DT1 and DT0 transferred from the transmitting circuit 40 in FIG. 14 .
  • the decoding signal T 5 is turned into the low level when the logical values DT1 and DT0 are “00”
  • the decoding signal T 6 is turned into the low level when the logical values DT1 and DT0 are “01”.
  • the data generator 58 includes NAND circuits 58 a , 58 b , 58 c , and 58 d , CMOS transmission gates 58 e , 58 f , 58 g , and 58 h , latches 58 l and 58 j , switching circuits 58 k and 58 l , and latches 58 m and 58 n.
  • the NAND circuits 58 a to 58 d are operated when the timing signal TDZ 4 is at the low level to make logical calculations of the decoding signals T 5 to T 8 , and inactivated when the timing signal TDZ 4 is at the high level to output the low level. Namely, data to be encoded is decided in synchronization with a rising edge of the timing signal TDZ 4 .
  • the timing signal TDZ 4 is the transmission signal which delays the latest timing signal TDZ 3 , as shown in FIG. 16 . For this reason, the data generator 58 can encode the received data quickly and securely, by using the timing signal TDZ 4 .
  • the CMOS transmission gates 58 e to 58 h are respectively controlled by outputs of the NAND circuits 58 a to 58 d .
  • a node ND0 changes to the high level by turning on the CMOS transmission gate 58 e , and changes to the low level by turning on the CMOS transmission gate 58 f .
  • a node ND 1 changes to the high level by turning on the CMOS transmission gate 58 g and changes to the low level by turning on the CMOS transmission gate 58 h.
  • the latches 58 l and 58 j respectively hold inverting values of the logic levels of the nodes ND0 and ND 1 .
  • the switching circuits 58 k and 58 l are turned on when the timing signal TDZ 4 is at the high level, and connect the latch 58 i and the latch 58 m , and the latch 58 l and the latch 58 n , respectively.
  • the latches 58 m and 58 n invert the latched values, and output these as the logical values RDT0 and RDT1.
  • the logic levels of the logical values RDT0 and RDT1 are the same as those of the nodes ND0 and ND 1 .
  • FIG. 18 shows the operations of the transmitting circuit 40 and the receiving circuit 42 .
  • the transmitting circuit 40 generates the standard timing signal TZ by using an external clock signal CLK which is supplied from the exterior of the chip.
  • CLK external clock signal
  • the timing that the standard timing signal TZ used in the receiving circuit 42 appears is made to be the same with that used in the transmitting circuit 40 .
  • the timing that the standard timing signal TZ used in the receiving circuit 42 appears is delayed corresponding to the load of the data bus line DATA.
  • the data which is read from the memory core is transmitted to the receiving circuit 42 in synchronization with the external clock signal CLK, and outputted to the exterior of the chip in synchronization with the next external clock signal CLK.
  • data (logical values DT1 and DT0) “00”, “01”, “10”, and “11” are respectively transmitted to the receiving circuit 42 in synchronization with the zeroth to the third external clock signals CLK.
  • the read amplifier 40 a in FIG. 15 operates in synchronization with a rising edge of the zeroth standard timing signal TZ to amplify the levels of the data DT0 and DT1.
  • the variable delay circuit 46 in FIG. 15 outputs the delay signals DLY 1 to DLY 4 in sequence, in synchronization with the standard reference signal TZ (not shown).
  • the switching circuit 46 e of the variable delay circuit 46 is turned on according to the decoding signal T 0 , and transmits the delay signal DLY 1 to the output part 48 . Then, the transmission signal SIG which corresponds to the logical value is outputted from the transmitting circuit 40 (FIG. 18 ( b )).
  • the delay circuit 50 inside the receiving circuit 42 in FIG. 16 outputs the timing signals TDZ 1 to TDZ 4 in sequence, in synchronization with the standard timing signal TZ (FIGS. 18 ( c ) and ( d )).
  • the timing of the rising edge of the transmitted signal SIG appears is earlier than the timing that the rising edges of the timing signals TDZ 1 to TDZ 4 appear.
  • the latch circuits 52 a , 52 b , and 52 c respectively take in the transmission signal SIG at the high level, and outputs the latch signals L 1 to L 3 at the high level and the latch signals /L 1 to /L 3 at the low level (not shown).
  • the decoder 56 inside the encoder 54 in FIG. 17 decodes the latch signals L 1 to L 3 and /L 1 to /L 3 , and changes only the decoding signal T 5 to the low level (FIG. 18 ( e )).
  • the outputs of the NAND circuits 58 b and 58 d of the data generator 58 change to the high level, and the CMOS transmission gates 58 f and 58 h are turned on.
  • both of the nodes ND0 and ND 1 are changed to the low level, and the logical values RDT0 and RDT1 are changed to the low level (FIG. 18 ( f )). Namely, the data which is read from the memory core is restored in the receiving circuit 42 . Thereafter, the logical values RDT0 and RDT1 are outputted to the exterior as reading data, in synchronization with the first external clock signal CLK.
  • the logical values “01”, “10”, and “11” are transmitted from the transmitting circuit 40 to the receiving circuit 42 in synchronization with the first to the third external clock signals CLK, similarly to the zeroth clock cycle.
  • the logical values are expressed by the time difference between the transition edge of the transmission signal SIG which is transmitted on the data bus line DATA and the transition edge of the standard timing signal TZ. For this reason, the logical values of the plurality of the bits can be transmitted by one signal line. Therefore, the number of the signal lines can be reduced as compared with the conventional art. Since only the small number of the signal lines is necessary, it is possible to reduce the number of the output circuits (output buffers) and the input circuits (input buffers) of the transmission signal. The number of the circuits to be operated decreases, and therefore, the power consumption can be reduced on both of the transmitting side and the receiving side of the transmission signal.
  • the logical value can be converted to the transmission signal by the simple transmitting circuit 40 and the transmission signal can be converted to the logical value by the simple receiving circuit 42 .
  • the transmitting circuit 40 and the receiving circuit 42 are formed on the same semiconductor memory device and the number of the data bus line DATA of the data read from the memory core is reduced. Thereby, it is possible to reduce the wiring area inside the semiconductor memory device. As a result of this, the chip size of the semiconductor memory device can be reduced, and the chip cost can be reduced.
  • FIG. 19 shows a third embodiment of the input/output interface and the semiconductor integrated circuit of the present invention.
  • the same numerals are given to the same elements as those in the second embodiment, and detailed explanations thereof are omitted.
  • a transmitting circuit 40 for transmitting data which is read from the memory cell on one end side of the chip and a transmitting circuit 40 for transmitting data which is read from the memory cell on the other end side of the chip are arranged separately from each other. Further, when a distance between two transmitting circuits 40 and a distance between a transmitting circuit 40 and a receiving circuit 42 are different, lengths of data bus lines DATA for connecting the transmitting circuits 40 and the receiving circuit 42 are different from each other.
  • the delay amount of the transmission signal SIG can be easily adjusted on the receiving circuit 42 side by using block selecting signals BK 0 Z and BK 1 Z for selecting the memory core and the transmitting circuits 40 , and resistors R 1 and R 2 .
  • block selecting signals BK 0 Z and BK 1 Z for selecting the memory core and the transmitting circuits 40 , and resistors R 1 and R 2 .
  • the standard timing signal TZ is delayed by the resistor R 2 whose resistance is high.
  • the standard timing signal TZ is delayed by the resistor R 1 whose resistance is low.
  • FIG. 20 shows a fourth embodiment of the input/output interface and the semiconductor integrated circuit of the present invention.
  • the same numerals are given to the same elements as those in the second embodiment, and detailed explanations thereof are omitted.
  • a transmitting circuit 40 and a receiving circuit 42 which are the same as those in the second embodiment are formed on both semiconductor integrated circuits (semiconductor chips) 60 and 62 .
  • the semiconductor integrated circuits 60 and 62 are mounted on, for example, a printed-wiring board, and connected to each other through a system bus on the printed-wiring board. Further, the semiconductor integrated circuits 60 , 62 transmit/receive data to/from each other.
  • the semiconductor integrated circuit 60 includes an SIG input buffer 64 (first input circuit), an SIG output buffer 66 (first output circuit), a TZ input buffer 68 (second input circuit), a TZ output buffer 70 (second output circuit), a TZ generating circuit 72 (signal generating circuit) and a clock input buffer 74 .
  • the SIG input buffer 64 outputs a transmission signal SIG which is outputted from the semiconductor integrated circuit 62 to the receiving circuit 42 .
  • the SIG output buffer 66 outputs the transmission signal SIG which is outputted from the transmitting circuit 40 to a data bus line DATA.
  • the TZ input buffer 68 outputs a standard timing signal TZ which is outputted from the semiconductor integrated circuit 62 to the receiving circuit 42 .
  • the TZ output buffer 70 outputs a standard timing signal TZOUT which is outputted from the TZ generating circuit 72 to the transmitting circuit 40 . Namely, the standard timing signal TZOUT which is generated in the TZ generating circuit 72 is not outputted directly to the system bus, but is outputted through the TZ output buffer 70 .
  • the TZ generating circuit 72 generates the standard timing signal TZOUT which synchronizes to an internal clock signal CLK 1 outputted from the clock input buffer 74 .
  • the clock input buffer 74 receives an external clock signal CLK from the exterior, and outputs it as the internal clock signal CLK 1 .
  • An input of the SIG input buffer 64 and an output of the SIG output buffer 66 are connected to the data bus DATA through a common external terminal.
  • the TZ input buffer 68 and the TZ output buffer 70 are connected to a signal line of the standard timing signal TZ through a common external terminal.
  • the data bus line DATA and the signal line of the standard timing signal TZ are allowed to transmit the transmission signals bidirectionally, which makes it possible to further reduce the wiring area of the signal lines.
  • the semiconductor integrated circuit 60 operates the SIG input buffer 64 and the TZ input buffer 68 when receiving the transmission signal SIG, and operates the SIG output buffer 66 , the TZ output buffer 70 , and the TZ generating circuit 72 when transmitting the transmission signal SIG.
  • the transmitting circuit 40 and the receiving circuit 42 are formed in the semiconductor integrated circuits 60 and 62 , whereby the transmission signal SIG can be transmitted bidirectionally by using the small number of the data bus lines DATA.
  • the input of the SIG input buffer 64 and the output of the SIG output buffer 66 are connected to the common external terminal, and the signal lines are made to transmit the transmission signals bidirectionally, so that the number of the signal lines can be reduced further.
  • the input of the TZ input buffer 68 and the output of the TZ output buffer 70 are connected to the common external terminal, and the signal line of the standard timing signal TZ is made to transmit the transmission signal bidirectionally, so that the number of the signal lines can be reduced further.
  • FIG. 21 shows a fifth embodiment of the input/output interface and the semiconductor integrated circuit of the present invention.
  • the same numerals are given to the same elements as those in the second and the fourth embodiments, and detailed explanations thereof are omitted.
  • This embodiment of the present invention is applied to a memory interface device 76 and a system bus.
  • the memory interface device 76 connects the system bus and a semiconductor memory device 78 .
  • the semiconductor memory device 78 is, for example, SDRAM of a conventional type (general-purpose memory).
  • the memory interface device 76 includes a receiving circuit 42 , a transmitting circuit 40 , an SIG input buffer 64 , an SIG output buffer 66 , a TZ input buffer 68 , a TZ output buffer 70 , a TZ generating circuit 72 , and a clock input buffer 74 , which are the same as those in FIG. 20 . Further, the memory interface device 76 includes an address input buffer 80 , a command input buffer 82 and a receiving circuit 42 for receiving an address signal AD. This embodiment of the present invention is applied to a data bus and an address bus.
  • the address input buffer 80 receives the address signal AD from the system bus in synchronization with a standard timing signal TZ, and outputs the received address to the receiving circuit 42 for the address.
  • the command input buffer 82 receives a command signal CMD from the system bus and outputs the received command to the semiconductor memory device 78 .
  • Data which is received in the receiving circuit 42 for the data and data (input/output data) which is read from the semiconductor memory device 78 and supplied to the transmitting circuit 40 are transmitted through the data bus line which is common to the input and the output.
  • the data and the address which are supplied through the system bus, are converted by the memory interface device 76 to the conventional data and the address, each of which consists of a plurality of bits, and supplied to the semiconductor memory device 78 . Then, a write operation or the like is performed. Further, the data consisting of the plurality of the bits, which is read from the semiconductor memory device 78 by a read operation, is converted by the memory interface device 76 to the interface of the present invention, and outputted to the system bus.
  • the command signal CMD and an external clock signal CLK may be supplied directly from the system bus to the semiconductor memory device 78 , without transmitting through the memory interface device 76 . However, it is possible to set the optimum timing thereof with reference to the data and the address, by transmitting through the command input buffer 82 and the clock input buffer 74 .
  • the present invention is applied not only to the interface of the data signal, but also to the interface of the address signal, so that the number of the signal lines of the system bus can be reduced as compared with the fourth embodiment, and the power consumption can be further reduced.
  • the present invention is applied to the memory interface device 76 , the general-purpose memory which has been mass-produced can be easily connected to the system bus to which the present invention is applied.
  • the example of expressing the logic of the transmission signal by the pulse signal is explained.
  • the present invention is not limited to the above embodiment.
  • either of the rising edge or the trailing edge of the transmission signal may be used to express the logic by combining the order.
  • the logic may be expressed by combining the order of the three or more transition edges of the transmission signals.
  • a three-state output circuit may be formed according to the numbers and the specifications of the transmitting circuit and the receiving circuit to be connected to the signal line, or an output buffer which is simply made of an inverter may be formed.
  • the present invention may be applied to an input/output interface for transmitting the data between function blocks which are mounted on the same chip.
  • the present invention may be applied to the transmission of an address signal which is outputted from a CPU to a memory, in the system LSI in which the CPU and the memory are mounted on the same chip.
  • the example of applying the present invention to the interface for transmitting the data which is read from the memory core to the peripheral circuit is explained.
  • the present invention is not limited to the above embodiment.
  • the present invention may be applied to an interface for transmitting writing data from the peripheral circuit to the memory core.
  • the transmitting circuit 40 and the receiving circuit 42 are formed on the separate semiconductor chips, whereby the number of the signal lines to be wired between the semiconductor chips can be reduced.
  • the semiconductor chips are mounted on the printed-wiring board, the area of the signal lines on the printed-wiring board can be reduced. As a result of this, the size of the printed-wiring board is reduced, so that the size of the system can be reduced and the cost of the system can be reduced.

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